What botanicals won't do...clearing up a few assumptions...

With all of the cool tanks we're seeing coming up, and a growing global interest in blackwater, botanical-style aquariums, we're seeing a lot of discussion about the "functional" aspects of botanicals. And with all of the discussion comes a little confusion, a lot of information, and some occasional misconceptions about what botanicals can do for our aquariums.

Today, I'd like to focus on what botanicals CAN'T do! Or at least, what they can't do as completely as many hobbyists tend to assume that they can! We're just gonna look at three things- but these are topics which seem to come up again and again, so I feel there worthy of a closer look.

Yeah, it's very important to clear up lingering (or emerging) misconceptions about the use of botanical materials in aquariums. As in so many areas of the hobby, the more people become involved in the process of utilizing them in their aquariums, the more we break through and clear up some of the confusions about them...And it's not like anyone was intentionally trying to mislead people over the years- I think it was more of a matter of us just making lots of assumptions and drawing conclusions from widely varying sources- often with questionable validity or accuracy.

So, in no particular order, here are some things that I think we need to address:

1) Botanicals cannot soften your water. I think it's easy to see how this one got started and tends to hang around a bit. Most botanical materials contain tannins and humic substances, which can drive down the pH in water with little to no carbonate harness. And of course, the tinted, soft acidic water in many natural habitats often has an abundance of leaves and botanicals present. I think that this gave a lot of hobbyists the impression that you could simply add some of these materials (leaves, etc.) into your tap water and create "Rio Negro-like" conditions easily!

Now sure, humic substances, tannins, and other compounds which color the water will be imparted to it when you add botanicals...

Yet, that's really only half of the story.

Botanicals cannot reduce the hardness of the water. This can only be accomplished with reverse osmosis or ion exchange( a process in which calcium and magnesium ions are "exchanged" for sodium or potassium ions.)

Reverse osmosis is a water treatment process which relies on a membrane which has pores large enough to admit water molecules, yet "hardness ions" such as Ca2+ and Mg2+ remain behind and are flushed away by excess water. The resulting product water is thus called "soft water"-free of hardness ions without any other ions being added. 

There is no substance you can add- natural or otherwise- directly to your water to soften it. 


2) Tinted water is not necessarily acidic. Once again, another assumption that no doubt arose from the aesthetics of blackwater itself. And it is easy to see how it got started...Much like the misconception that botanicals soften the water, it was often assumed by hobbyists that the brownish tint imparted to the water by leaves and botanicals somehow implied that it is acidic. Yes, these materials contain substances that can reduce the pH in water with low to negligible carbonate hardness.

However, the tannins, which are the substances which tint the water, cannot "overcome" the Calcium and Magnesium ions, and drive down the pH significantly in water with high levels of these carbonate hardness present. It simply is putting more materials into the water (which are often detectible by TDS meters in aquariums). And, as we've discussed before, there are natural habitats, such as the Tapajos, which have essentially clear water, yet are rather soft and acidic. 


3) Catappa leaves can "cure fish diseases." Well, this is one of the favorites which has been perpetuated for years (often by people who sell leaves online and elsewhere -hey, I'm in that group, huh?)- and it actually has some validity to it. It has been known for many years by science that botanicals like catappa leaves (and others) have substances in their tissues which do have some potential medicinal functions, like saponins phytosterols, punicalagins, etc.  Fancy names that sounds really cool- these are often bounced around on hobby sites as the "magic elixir" for a variety of fish ailments and maladies.

Now, I can't entirely beat the crap out of this idea, as these compounds are known to provide certain health benefits in humans. and for a long time, it was anecdotically assumed that they did the same for fishes. And believe it or not, there have been studies that show benefits to fishes imparted by substances in catappa and other leaves. I stumbled across a study conducted in Thailand with Tilapia concluded  that Catappa extract was useful at eradicating the nasty exoparasite, Trichodina, and the growth of a couple of strains of Aeromonas hydrophila was also inhibited by dosing Catappa leaf extract at a concentration of 0.5 mg/ml and up. In addition, this solution was shown to reduce the fungal infection in Tilapia eggs!

And it is now widely accepted by science that humic substances (such as those present in botanicals) are thought to have a wide range of health benefits for fishes in all types of habitats. We've covered this before in a great guest blog by Vince Dollar, and the implications for the hobby and industry are profound. Although they are not the "cure all" that many vendors have touted them as, leaves and other botanicals do possess a wide range of substances which can have significantly beneficial impact on fish health.

Of course, there are many others which arise from time to time- but those are "the big three" that we seem to hear about a lot. And, as we've seen, these are not entirely erroneous; however, it's important NOT to make assumptions about these materials, and to assume that they are "miraculous things" we can add to our tanks to do achieve smashing success.

The fact is, we still don't fully understand all of he affects- mostly good- but some possibly not so good- about the use of botanicals in aquariums. We have seen a LOT of instances of seemingly "spontaneous" (or at least, rather rapid) spawnings of fishes which have otherwise eluded the aquarists' efforts- shortly after introducing botanicals to their tanks.

Is this a result of some "substances" present in the botanicals? Is it a lowering of the pH in a softer-water aquarium? IS it those humic substances? Shock or some type of stress response? (!) Or could it be just a coincidence? It could be all of the above- however, I must admit that the number of times we've seen and heard this happen to us and others leads me to believe that there literally IS "something in the water!" Exactly what, of course- and how it influences these events is yet to be fully determined! 

And isn't that just the kind of stuff that keeps hobbyists coming back for more...searching, experimenting, tweaking?

Yeah, it is. And with more "technique" than ever before starting to replace the "dump and pray" method of using botanicals in aquariums, we're seeing more and more interesting results that simply go beyond just enjoying the unique aesthetics offered by blackwater, botanical-style aquariums. We're starting to see some interesting effects on the health and well-being of many species of fishes. We're learning about the value of replicating (to some extent) the natural conditions which our fishes have adapted to for eons.

And perhaps most important- we're taking a good, long look at many aspects of the precious- and often endangered- natural habitats of our fishes. This search for knowledge and appreciation of nature will not only benefit the hobby, but quite possibly the ecosystem of our home planet, as we gain a better understanding of the dynamics of blackwater habitats and the need to preserve and protect them as havens of life.


Oh, and we're having some FUN, too!

Stay bold. Stay experimental. Stay open-minded, yet skeptical. Stay diligent...

And Stay Wet.


Scott Fellman

Tannin Aquatics 



Scott Fellman
Scott Fellman


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